1. Technical Field
This invention relates generally to a broadband communication system which makes use of ordinary twisted pair telephone wires already installed in a facility such as an office building. The invention provides for bidirectional transmission of full-motion color video, stereo audio, and data signals over ordinary telephone wires without interfering with existing telephone equipment. One application of the invention is video teleconferencing between two or more telephone users in an office connected through a telephone switch such as a Private Branch Exchange (PBX).
2. Related Information
Conventional video teleconferencing systems often include line services for parties to a teleconference, bridging services which coordinate calls among parties at multiple locations, and public room services which provide video conferencing equipment to the public on a usage charge basis. Presently available systems include permanently installed systems, portable boardroom systems, and desktop systems. However, such systems are expensive and often require the installation of high bandwidth wiring and related equipment. Less expensive systems typically provide inferior video quality which is unacceptable for videoconferencing purposes.
Various techniques for transmitting video information over ordinary telephone wires are well known. For example, U.S. Pat. No. 5,164,982 to Davis discloses a system which transmits text, graphics, and picture data over existing telephone lines. U.S. Pat. No. 5,199,061 to Kim discloses a system which transmits freeze frame video between users over standard telephone lines. U.S. Pat. No. 5,283,637 to Goolcharan contemplates a system which allows for transmission of full motion color video, voice and data over ordinary telephone wires. U.S. Pat. No. 5,541,640 to Larson discloses a so-called xe2x80x9cvideophonexe2x80x9d which allows simultaneous transmission of audio and video over a standard telephone line.
Unfortunately, providing two-way videoconferencing capabilities in an interoffice environment over ordinary telephone wires is presently quite expensive. In the current market, video application systems with high-resolution, realistic images can cost more than $15,000 for a unit that operates at only one location within a facility. Desktop system alternatives, while generally cheaper, provide degraded images and limited audio quality. Moreover, complicated infrastructure changes are often necessary to support more than a few units. Existing systems also use proprietary techniques which cannot support standard communication techniques such as ISDN and ATM.
In addition to their high cost, other problems with presently available videoconferencing systems include an inability to provide stereo audio, low quality audio transmission, lack of color (for some systems), and inability to support video retrieval applications. Due partly to these and other shortcomings, videoconferencing systems have not seen widespread use.
The present invention overcomes the aforementioned problems by providing an inexpensive method and apparatus for switching high quality video, data and audio signals throughout a conventional office telephone system over existing telephone wires. Applications of the present invention include video teleconferencing, broadcasting of program materials within an office, remote video retrieval, remote monitoring, and collaboration on documents and spreadsheets from different locations among others. Because the invention makes use of existing telephone wiring and switching facilities, substantial cost savings can be achieved while providing high quality video transmission.
The invention enables an existing PBX or Centrex business telephone system to be easily upgraded to provide broadband communications capabilities. The invention takes advantage of the fact that much of the bandwidth available within an office building telephone wiring system is unused. Conventional telephone systems typically only use about 5 KHz of bandwidth for an analog telephone and less than 1 MHZ for a digital telephone. Normal twisted pair wiring within an office building, however, can support up to 20 MHZ or so for category 3 cable and 150 MHZ or so for category 5 cable.
Various embodiments of the present invention provide for the transmission and reception of full-motion high quality video, CD-quality stereo audio, and high speed data to and from telephone users in an office building. The invention provides such services over the same basic wiring that serves existing telephone systems and therefore avoids costs associated with new wiring or infrastructure. The invention is compatible with most digital and analog telephony systems sold by leading PBX and telephone vendors, and provides interfaces for newer Integrated Services Digital Network (ISDN) phone systems and Asynchronous Transfer Mode (ATM) networks. Users of the invention can operate video-type applications such as teleconferencing while simultaneously engaging in a telephone conversation over the same telephone wires.
Various embodiments of the system generally include five components: (1) a plurality of video modems which modulate and demodulate video signals in an efficient format over interoffice telephone wires; (2) a broadband data switch which handles set-up and tear-down of video data paths over the telephone wires; (3) a plurality of video teleconferencing stations such as personal computers; (4) a video server; and (5) software which operates across the various components.
A broadband data switch in accordance with the invention can accommodate a variety of interfaces including video modem cards, ATM switches, ISDN lines, and multipoint conference bridges. In various embodiments, the broadband data switch does not rely on a local area network but instead uses ordinary telephone lines for communication. However, the invention is not limited in this respect and thus the invention can be practiced over a conventional LAN such as Ethernet.
An internal video conference call between two or more stations within 2,500 feet of each other (a distance that would permit calls within the largest high-rise buildings) can be connected using the building""s existing telephone lines via the broadband data switch. The telephone can be used for incoming and outgoing calls, even while the line is being used for video conferencing or other video applications.
The invention permits any combination of high-quality audio, video, and data to be transmitted over ordinary telephone lines which are shared with an existing telephone switch.
Other features and advantages of the invention will become apparent with reference to the following detailed description and the figures.